The present invention relates to a data transmission system for performing data exchange between a local station and remote terminals, such as DSUs (Data Service Units), which are star-connected to the local station, and particularly to a terminal management method of the data transmission system wherein data transmission from a remote terminal to the local station (hereinafter called upward communication) is performed according to a TDMA (Time Division Multiple Access) system and data transmission from the local station to the remote terminals (hereinafter called downward communication) is performed according to a TDM (Time Division Multiplex) system, making use of cells having fixed length.
In data transmission systems having a star connection, such as used in a POS (Point Of Sales) system, there are systems wherein data exchange is performed making use of fixed-length packets called cells, including main data cells for transmitting data to be communicated and control data cells used for controlling or status-monitoring of the data transmission system. These cells have header information fields for loading control information such as destination of the cells, kinds of the cells or transmission permission to remote terminals.
To avoid collisions among cells transmitted upward from remote terminals which are star-connected, cell transmission control of the remote terminals, such as transmission permission control, band-width control or cell-phase control, is performed in the local station, and the remote terminals transmit upward cells under control of the local station.
For efficiently performing the cell transmission control of each individual remote terminal, usually an identification number, which is unique in a closed area consisting of a local station and remote terminals connected thereto, is assigned to each of the remote terminals, besides their own identifiers, such as product numbers. The identification numbers assigned to the remote terminals are registered in the local station in connection with the product numbers, for example, obtained from the remote terminals, and the assigned identification numbers are memorized by the remote terminals to be referred to afterwards for discriminating the same.
As to acquisition of the proper identifier such as the product number of the remote terminal and assignment of the local identification number, there have been proposed some methods.
In a Japanese patent application laid open as a Provisional Publication No. 036130/'89, there is disclosed a prior art to assigning an identification number to a radio-telephone terminal from a relay-station, in order to avoid costs of setting the identification number to the relay-station equipment and the radio-telephone terminals in their production factory at the shipping, and in a Japanese patent application laid open as a Provisional Publication No. 303174/'94, a wireless data communication system is disclosed, wherein polling to a wireless terminal is automatically suspended when the wireless terminal leaves the system and it is started again automatically when the wireless terminal returns to the system.
However, according to the former prior art, the proper identifier such as the product number of the remote terminal should be beforehand registered manually in the relay-station for assigning the local identification number automatically in connection with the proper identifier.
In the latter prior art, polling controlled can be performed automatically for improving band-width efficiency according to numbers of active wireless terminals. However, the proper identifiers of the wireless terminals are not managed, and therefore, the system could not recognize automatically a wireless terminal newly installed in the system.
Further, the data transmission system as above mentioned, wherein the upward communication is performed according to the TDMA system and the downward communication is performed according to the TDM system, needs specific communication control, and so, prior arts as above described cannot be applied as they are.